In response to the critical rise in multidrug-resistant (MDR) bacteria, the LAMEXA-LAMA laboratory at the University of Panama has conducted research focused on the search for bacteriophages as a therapeutic and sanitary alternative. This study involved the isolation and biological characterization of lytic phages specific to Klebsiella pneumoniae and Serratia marcescens, utilizing hospital and urban wastewater matrices from the Dr. Arnulfo Arias Madrid Hospital Complex, the Cinta Costera pumping station, and the Panama City Wastewater Treatment Plant (WWTP). The bacterial strains used were previously identified via the Vitek-2 system and endpoint PCR. As a result, 12 phages (7 for K. pneumoniae and 5 for S. marcescens) were isolated and purified using the double-layer agar technique, with subsequent tests conducted using stock concentrations of 10⁷ PFU/mL. Phenotypic evaluation demonstrated that 57% of the K. pneumoniae phages and 20% of the S. marcescens isolates exhibit effective lytic activity against clinical and environmental strains with confirmed MDR profiles. Furthermore, candidates with exceptional physicochemical stability were identified, maintaining viability across a pH range of 3 to 11, thermal resistance up to 60°C, and tolerance to 90% chloroform concentrations. Additionally, phages showed suppression indices of 50% at an MOI of one. These findings lay the groundwork for the genomic sequencing and bioinformatics analysis phase, aimed at validating their application in phage therapy, biological control, and water sanitation protocols. This project seeks to consolidate a robust line of research extending to other pathogens within the ESKAPE group, strengthening Panama's scientific infrastructure against modern medical threats.